1. Field of the Invention
The present invention relates to a thin film magnetic recording head which is used for, for example, a floating magnetic head, which is adaptable to track narrowing, and which can appropriately suppress the occurrence of write fringing and magnetic flux saturation, and a method of manufacturing the thin film magnetic head.
2. Description of the Related Art
A thin film magnetic head mounted to a hard disk or the like comprises, for example, an inductive head for writing signals on a recording medium such as a hard disk, and a MR head for reading signals from the recording medium.
The inductive head generally comprises upper and lower core layers made of a magnetic material, and a coil layer for inducing a recording magnetic field in the core layers so that a magnetic signal is recorded on a recording medium by a leakage magnetic field between the core layers.
In recent years, the track width Tw of the inductive head has been decreased to comply with the requirement for narrowing a track accompanying an increase in recording density. The track width Tw is determined by the width dimension at the end of the upper core layer exposed in a surface (ABS) facing the recording medium.
The upper core layer is conventionally formed by, for example, a so-called frame plating process. In this frame plating process, a resist layer is patterned in the shape of the upper core layer, and a magnetic material used as a material for the upper core layer is plated in the pattern. Then, the resist layer is removed to complete the upper core layer having an end with the track width Tw.
However, the frame plating process is very difficult to pattern the resist layer with the small track width Tw because of the resolution limit of exposure in pattering the resist layer. This problem will become significant with further increases in recording density in future.
U.S. Pat. No. 5,652,687 discloses the structure of an inductive head formed by a process different from the above-described frame plating process, and a method of producing the inductive head. FIG. 10 shows the frame plating process disclosed in U.S. Pat. No. 5,652,687.
In FIG. 10, reference numeral 102 denotes a lower pole layer (lower core layer) on which a notch structure 120 made of silicon dioxide or the like is formed. FIG. 11 is a perspective view showing the shape of the notch structure 120, a trench 148 being formed in the notch structure 120. A pole tip layer P1 (T), a gap layer G, and a pole tip layer P2 (T) are laminated in the trench 148.
Furthermore, the pole tip 108 of an upper pole layer (upper core layer) 104, which has a width dimension larger then the width dimension of the pole tip layer P2 (T), is formed on the pole tip layer P2 (T) and the notch structure 120.
This publication discloses that the production process can provide a thin film magnetic write head having a sub-micron track width. The publication also discloses that as shown in FIG. 10, the pole tip 108 having a width dimension larger then the width dimension of the pole tip layer P2 (T) is formed on the pole tip layer P2 (T), and magnetic saturation accompanying track narrowing can thus be prevented by the formation of the pole tip 108.
The inductive head shown in FIG. 10 has the function to write signals on the recording medium by means of a leakage magnetic field produced between the core layers. However, since the pole tip 108 is formed at right angles on the upper edge of the pole tip layer P2 (T), the leakage magnetic field reaches from the pole tip 108 to the pole tip layer PI (T), as shown by broken lines in FIG. 10. As a result, write fringing (writing blot) which occurs on both sides of the track width Tw is easily formed on the recording medium.
The occurrence of write fringing makes it impossible to precisely detect the track position on the written recording medium, thereby causing tracking servo error. Particularly, in high-density recording, the track pitch is decreased to increase the influence of write fringing.
The problem of write fringing significantly occurs when a leakage magnetic field reaches from the pole tip 108 to the pole tip layer P2 (T). A possible method of suppressing the occurrence of write fringing is to decrease the width dimension of the pole tip 108.
However, a decrease in the width dimension of the pole tip 108 causes a problem of magnetic saturation, thereby decreasing the magnetic flux density and deteriorating recording properties.
Therefore, the inductive head disclosed in U.S. Pat. No. 5,652,687 does not have a structure which can simultaneously prevent the occurrence of write fringing and magnetic saturation.
FIG. 24 is a partial front view showing a manufacturing step of a thin film magnetic head which is improved for suppressing the occurrence of write fringing.
In the step shown in FIG. 24, an insulating layer 5 is formed on a lower core layer 1 made of a magnetic material, and a trench 3 is formed in the insulating layer 5 to form the insulating layer 5 in the same shape as the notch structure 120 shown in FIG. 11.
As shown in FIG. 24, a resist layer 4 is coated on the surface of the insulating layer 5 by spin coating to fill a portion of the trench 3 of the insulating layer 5 with the resist layer 4.
Since the trench 3 formed in the insulating layer 5 is filled with the resist layer 4, the thickness of the resist layer 4 formed on the insulating layer 5 decreases toward the trench 3.
In the state shown in FIG. 24, the surface of the insulating layer 5 coated with the resist layer 4 is etched off, for example, by ion milling to cut the both edges 5a of the insulating layer 5 in the vicinity of the trench 3. As a result, inclined surfaces 5b are formed at both edges 5a of the insulating layer 5 so that the distance between the inclined surfaces 5b decreases toward the lower core layer 1, as shown in FIG. 25.
After the resist layer 4 shown in FIG. 25 is completely removed, the same layers as the pole tip layer P1 (T), the gap layer G and the pole tip layer P2 (T) shown in FIG. 10 are laminated in the trench 3 shown in FIG. 25, and the same layer as the pole tip 108 shown in FIG. 10 is further formed on the pole tip layer P2 (T).
In this manufacturing method, the layer corresponding to the pole tip 108 shown in FIG. 10 is formed along the inclined surfaces 5b of the insulating layer 5. Since the layer corresponding to the pole tip 108 has a shape in which the width gradually increases away from the gap layer G, the leakage magnetic field shown by the broken lines in FIG. 10 less occurs, thereby preventing the occurrence of write fringing on the both sides of the track width Tw.
However, in the process comprising forming the inclined surfaces 5b shown in FIGS. 24 and 25, the trench 3 is formed in the insulating layer 5, and thus a variation easily occurs in the thickness of the resist layer 4 formed on the insulating layer 5. Such a variation in the thickness of the resist layer readily causes variations in the inclination angle and the shape of the inclined surfaces 5b formed in the insulating layer 5, thereby making quality unstable.
The present invention has been achieved for solving the above problems, and an object of the present invention is to provide a thin film magnetic head which is adaptable to track narrowing and which can effectively prevent write fringing and relieve magnetic flux saturation.
Another object of the present invention is to provide a thin film magnetic head for readily forming an inductive head with high reproducibility which can effectively suppress the occurrence of write fringing and magnetic flux saturation, and a method of manufacturing the thin film magnetic head.
A further object of the present invention is to provide a method of manufacturing a thin film magnetic head which is adaptable to track narrowing, and which can readily form inclined surfaces for effectively preventing write fringing with high reproducibility.
The present invention provides a thin film magnetic head comprising a lower core layer made of a magnetic material, an upper core layer made of a magnetic material, a gap layer for magnetically insulating the lower core layer from the upper core layer, and an insulating layer located between the lower core layer and the upper core layer, all of which are exposed in a surface facing a recording medium, wherein a trench is formed in the insulating layer to lead from the surface of the insulating layer to the lower core layer and further extend from the surface facing the recording medium in the height direction , the trench comprises a track-width region which defines the track width from the top of the lower core layer to a predetermined height, and an inclined region having inclined surfaces so that the width dimension of the trench gradually increases from the upper end of the track-width region to the surface of the insulating layer, the gap layer is located in the track-width region, and a portion of the upper core layer is formed to extend from the inclined surfaces formed in the trench in the direction away from the lower core layer.
In the present invention, as described above, the trench comprises the track-width region, which defines the track width from the upper side of the lower core layer to the predetermined height, and the inclined region which has the inclined surfaces so that the width dimension of the trench gradually increases from the upper end of the track-width region to the surface of the insulating layer, and a portion of the upper core layer is formed to extend from the inclined surfaces formed in the trench in the direction away from the lower core layer.
In the present invention, therefore, the upper core layer is formed on the inclined surfaces which are formed so that the width dimension of the trench of the insulating layer gradually increases, and thus the width dimension of the upper core layer can be formed with a width dimension larger than the track width Tw. It is also possible to suppress magnetic flux saturation, and appropriately separate the upper core layer from a lower pole layer formed in the track-width region of the trench and magnetically connected to the lower core layer, thereby appropriately suppressing the occurrence of write fringing.
In the present invention, the upper core layer is preferably formed on the inclined surfaces to reach the boundaries between the inclined surfaces and the surface of the insulating layer, and further extend from the boundaries in the direction away from the lower core layer.
In the present invention, the upper core layer is preferably formed to extend perpendicularly to the planar direction of the lower core layer.
The insulating layer may be formed so that the thickness gradually decreases from each of the boundaries between the inclined surfaces and the insulating layer surface in the direction away from the trench. In this case, the surface of the insulating layer may be concavely curved.
In the present invention, preferably, the lower pole layer is formed at the bottom of the trench formed in the insulating layer to be magnetically connected to the lower core layer, and the gap layer is formed on the lower pole layer, and an upper pole layer is formed on the gap layer to be magnetically connected to the upper core layer. The film structure formed in the track-width region may be changed to another structure.
In the present invention, in the above-described construction, both the lower pole layer and the upper pole layer are preferably formed in the track-width region of the trench.
The present invention also provides a method of manufacturing a thin film magnetic head comprising a lower core layer made of a magnetic material, and an upper core layer made of a magnetic material and formed opposite to the lower core layer with a nonmagnetic gap layer provided therebetween on a surface facing a recording medium, the method comprising the steps of forming, on the lower core layer, an insulating layer having a trench having an internal width dimension corresponding to a track width in the height direction from the surface facing the recording medium, continuously laminating a lower pole layer magnetically connected to the lower core layer, a gap layer, and an upper pole layer magnetically connected to the upper core layer in the trench, forming inclined surfaces before or after the laminating step so that the width dimension of the trench gradually increases from an intermediate position of the trench, forming a resist layer on the insulating layer by exposure development with a space wider than the width dimension of the trench on the surface of the insulating layer to expose the surface of the upper pole layer, the inclined surfaces of the trench formed in the insulating layer, and a portion of the surface of the insulating layer in the space of the resist layer, forming an upper core layer in the space of the resist layer and removing the resist layer, and etching the side surfaces of the upper core layer by ion milling so that the side surfaces of the upper core layer are connected to the tops of the inclined surfaces.
In the manufacturing method of the present invention, the resist layer required for forming the upper core layer and having the space wider than the width dimension of the trench formed in the insulating layer is formed by exposure development.
Namely, in the present invention, by exposure development, the coated resist layer is removed from the trench of the insulating layer to leave only the resist layer which is coated to a substantially constant thickness on the flat surface of the insulating layer. Therefore, in exposure development, irregular reflection less occurs due to a difference in focus, thereby forming the resist layer in a stable shape on the surface of the insulating layer.
Since not only the surface of the upper pole layer and the inclined surfaces of the trench, but also a portion of the surface of the insulating layer are exposed in the space of the resist layer, the upper core layer formed in the space of the resist layer by plating extends not only to the surface of the upper pole layer and the inclined surfaces of the trench, but also to the surface of the insulating layer. In this state, a leakage magnetic field occurs between the upper core layer formed to extend to the surface of the insulating layer and the lower pole layer, thereby possibly causing write fringing. Therefore, in the present invention, the side surfaces of the upper core layer are etched by ion milling in the next step to remove the portion of the upper core layer, which is formed on the surface of the insulating layer, so that the side surfaces of the upper core layer are connected to the tops of the inclined surfaces of the trench.
The thin film magnetic head of the present invention manufactured as described above is adaptable to track narrowing, and can effectively prevent write fringing and suppress magnetic flux saturation.
The manufacturing method of the present invention can easily form, with high reproducibility, the upper core layer which has a significant influence on the problem of write fringing and magnetic flux saturation, thereby improving yield.
Furthermore, in the present invention, the surface of the insulating layer may be etched by ion milling at the same time as ion milling for etching the side surfaces of the upper core layer to form a concavely curved surface so that the thickness of the insulating layer gradually decreases from each of the boundaries between the surface of the insulating layer and the inclined surfaces of the trench in the direction away from the trench.
In the present invention, the upper core layer is preferably formed perpendicularly to the planar direction of the lower core layer by the ion milling.
The present invention further provides a method of manufacturing a thin film magnetic head comprising a lower core layer made of a magnetic material, and an upper core layer made of a magnetic material opposite to the lower core layer with a nonmagnetic gap layer formed therebetween on a surface facing a recording medium, the method comprising the first step of forming an insulating layer having an internal width dimension corresponding to a track width dimension in the height direction from the surface facing the recording medium, the second step of forming a lower pole layer in the trench by plating so that the lower pole layer is magnetically connected to the lower core layer, the third step of forming a gap layer made of a nonmagnetic material on the lower pole layer in the trench, the fourth step of forming an upper pole layer on the gap layer in the trench by plating, the fifth step of forming a resist layer having a space having a width dimension wider than the trench of the insulating layer on the insulating layer to expose portions of the insulating layer at both sides of the upper pole layer in the trench, the sixth step of cutting away the portions of the insulating layer, which are exposed in the space of the resist layer, to form inclined surfaces in the insulating layer so that the distance therebetween gradually increases from the upper pole layer side to the surface of the insulating layer, the seventh step of removing the resist layer, and the eighth step of forming an upper core layer by plating so that the upper core layer is magnetically connected to the upper pole layer in the inclined surfaces of the insulating layer.
For example, the fourth step comprises forming the upper pole layer by plating to form steps between the surface of the upper pole layer and the surface of the insulating layer so that the surface position of the upper pole layer is lower than the surface position of the insulating layer, and the sixth step comprises cutting away the steps of the insulating layer to form the inclined surfaces.
In the sixth step, inclined surfaces can be formed in the upper pole layer to be connected to the inclined surfaces formed in the insulating layer.
In this case, the above-described steps may be either formed or not between the surface of the upper pole layer and the surface of the insulating layer.
A nonmagnetic metal material is selected for the gap layer so that the gap layer can be formed by plating in the third step.
In this case, as the nonmagnetic metal material, at least one material can be selected from NiP, NiPd, NiPt, NiRh, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
By selecting the nonmagnetic metal material for the gap layer, not only the lower pole layer and the upper pole layer but also the gap layer can be formed with uniform thicknesses in the trench.
In the present invention, as described above, the lower pole layer, the gap layer and the upper pole layer are continuously formed by plating in the trench of the insulating layer formed on the lower core layer, and the inclined surfaces are formed on both sides of the upper pole layer so that the distance therebetween increases from the surface of the upper pole layer to the surface of the insulating layer.
In the present invention, as described above, the lower pole layer, the gap layer and the upper pole layer are buried in the trench formed in the insulating layer so that the resist layer used for forming the inclined surfaces can be formed on a substantially flat surface (on the insulating layer and the upper pole layer). Therefore, the resist layer can be formed to a uniform thickness, thereby forming the inclined surfaces in a predetermined shape at both side edges of the trench of the insulating layer with high reproducibility and controllability.
Since the inclined surfaces having the predetermined shape can be easily formed with high reproducibility, the distance between the upper core layer and the lower pole layer can be appropriately set in forming the upper core layer on the inclined surfaces, thereby making adaptable to track narrowing, and permitting manufacture of inductive heads causing no write fringing with high yield.